Rumen Motility as Influenced by Physical Form of Oat Hay

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Abstract
The effect of oat hay, fed in the long condition and after grinding through 1/4 in or 3/32 in hammermill screens, on the rumen motility of steers was studied. In one experiment all bedding was removed from the steers when the 3/32 in hay was fed. Significant differences (P< .01) in rumen contraction amplitude existed between the steers on all the diets except between those on the 2 3/32 in hay diets. The difference in the rumen contraction frequency of the steers on diets of long and 1/4 in hay was not statistically significant; however, both of these diets produced rumen contractions which were significantly (P< .05) more rapid than those observed for the steers on the 3/32 in hay diets. The average time required for the rumen contraction amplitude to become uniform when the diet was changed from long hay to 3/32 in hay was 4 weeks; 1/4 in hay to 3/32 in hay, 5 weeks; 3/32 in hay to long hay, 6 weeks; and when the sawdust bedding was removed from the calves on the 3/32 in hay, 2 weeks. Frothy rumen ingesta and frequent bloating were observed in steers receiving the 3/32 in hay diets; one death occurred. Scabrous materials in the diet may maintain or reinforce the tonic activity of the motor neurons responsible for rumen motility.